1. Field of the Invention
This invention relates to a semiconductor light-emitting device, and, in particular, to a semiconductor light-emitting device formed of a combination of a semiconductor light-emitting element and a visible-light luminescent element containing a phosphor.
2. Description of the Related Art
In recent years, there have been proposed various kinds of light-emitting devices wherein a semiconductor light-emitting element is combined with a phosphor (for example, see JP-A 2005-205195 and JP-A 2006-210887). The phosphor to be used in these light-emitting devices is capable of absorbing excitation light emitted from a semiconductor light-emitting element and capable of emitting light having a different wavelength from that of the excitation light, thus functioning as a light source.
JP-A 2005-205195 describes a light-emitting device excellent in luminescence and color rendering. This light-emitting device employs an optical fiber as an optical waveguide of the excitation light and is constructed such that the optical fiber is provided at its distal end with a phosphor and that the light from the light-emitting element is irradiated onto the phosphor through the optical fiber.
JP-A 2006-210887 describes a light-emitting device excellent in light extraction efficiency, this light-emitting device being provided with a semiconductor light-emitting element capable of emitting excitation light and with a dispersion member having the phosphor dispersed therein. In this light-emitting device, the light to be emitted from the phosphor in the dispersion member is extracted from the excitation light incidence side of the dispersion member.
These light-emitting devices described in these JP-A 2005-205195 and JP-A 2006-210887 however fail to take into consideration the following problems. Namely, in these light-emitting devices, the excitation light is concentrated at one point of the phosphor, creating a point light source exhibiting high brightness and increasing excitation density, thereby raising various problems such as the decrease in light-emitting efficiency and the deterioration of materials due to the generation of heat resulting from the emission of light. Because of these problems, it is impossible to sufficiently increase the excitation density and to utilize a light-emitting element capable of outputting a high-energy beam, so that these light-emitting devices cannot be applied to an apparatus requiring a high luminous flux such as a lighting apparatus, an image display apparatus, etc.